The present invention relates to turn-signal systems for vehicles, and more particularly to an automatic cancelling system for such turn-signal systems.
Various vehicles, such as automobiles, are in general equipped with an automatic turn-signal cancelling device, sometimes referred to as an automatic winker or flasher cancelling device. In automobiles, steering wheels commonly are used and the cancelling device is arranged to measure by mechanical means a certain return amount of the steering wheel from the maximum steering position, and then the turn-signal is automatically cancelled when the measured return movement of the steering wheel exceeds a set level. Such arrangements take advantage of the relatively large degree of rotation of the steering wheel or large steering angle involved with automobiles.
On the other hand, while the application of such automobile automatic turn-signal cancelling devices to motorcycles has been considered, it is relatively difficult because of the different steering arrangement for motorcycles which involves not only the steering angle of the handle bars but also the shift or tilt angle of the front wheel of the motorcycle. The shift or tilt angle of the front wheel is about the same as the steering angle of the handle bars and, therefore, the amount of change in the steering angle of the handle bars required in changing the running direction of the motorcycle is relatively small. Furthermore, the arrangements used in automobiles have further disadvantage if applied to motorcycles because although the steering angle is measured with respect to the center position of the handle bars, accurate determination of the center position of the handle bars of a motorcycle is difficult in the manufacture and use of the motorcycle, thereby resulting in difficulties in accurately measuring the steering angle. Additionally, when the running speed of the motorcycle is reduced, and after a turn signal has been turned on but before a sufficient change in the running direction of the motorcycle, the turn signal may be cancelled because of the necessary movement by the operator of the handle bars for maintaining balance. That is, these low frequency pertubations of the handle bars can cause the turn-signal to be cancelled prior to when they should be cancelled in practice.